I am pretty sure that the answer is A. For me A had "The substrate was used up by the time the temperature reached 60°C".
Explanation: Both A's have similar questions, I'm really sorry if its correct
The enzyme has changed shape because of high temperature.
Enzymes are biological catalysts in living organisms that speed up the rate of chemical reactions.
High temperature changes the shape of enzymes.
Increase or high temperature lead to decrease in enzymes activities. This is due to enzyme protein been denatures by high temperature which is the breaking of molecular bonds within the enzyme protein. When the enzymes bonds are broken, the shape of the enzymes changes and they no longer act as catalysts.
The correct answer is option B.
At 60 to 70 degrees the reaction stops, due to the rise of temperature more than its optimum temperature. At high-temperature molecules of enzyme vibrate more, this vibration breaks the bonds that determine the shape of the enzyme in shape.
The shape of the active site of enzyme changes due to this and the substrate is not fit together with it and the reaction stops.
Thus, the correct answer is - B.
The correct option is B. The Enzyme or substrate has been changed.
Enzymes can be described as biological catalysts which speed up a reaction. Each enzyme is specific for a particular substrate. Enzymes work best at a particular pH and temperature known as optimum pH and optimum temperature.
As the temperature is raised, the working of the enzyme enhances. It becomes most efficient at a particular temperature which is known as the optimum temperature. If the temperature is raised beyond this optimum temperature, then the working of the enzyme starts to decline. Eventually, the enzyme loses its shape and is not able to fit the substrate into its active site. So, activity of the enzyme stops.
The enzyme has changed shape because of the high temperature.
Relative Rate of Enzyme...